Urolithin A for Strength & Function in Aging

Reviewed by SOMA HEALTH's Medical Research Team

Strength is not a single muscle number. It is the quiet capacity to stand from a low chair, carry groceries up a flight of stairs, and catch yourself when a curb surprises you. That capacity tends to erode slowly with age, and a growing body of research has begun to ask whether the health of our mitochondria is part of the story. This guide looks at what urolithin A is, what human trials have actually measured, and how to think about it honestly if strength and physical function are on your mind.

What actually changes in muscle as we age

From roughly the fourth decade onward, most adults lose skeletal muscle mass and strength gradually, with the pace often accelerating after 60. Clinicians call the age-related decline in muscle mass, strength, and function sarcopenia. Strength typically falls faster than sheer size, which is why an older adult can look reasonably muscled yet struggle to rise from the floor. Several changes stack up at once: fewer and smaller fast-twitch fibers, reduced motor-unit recruitment, more intramuscular fat, and lower overall physical activity.

Underneath these visible shifts sits a cellular one. Muscle is metabolically expensive tissue, and it depends on mitochondria, the compartments that convert food and oxygen into usable energy. Research on aging muscle has repeatedly found that mitochondrial content and quality tend to decline over time, and that lower muscle mitochondrial capacity tracks with slower walking, weaker legs, and greater fatigue. Mitochondria are not the whole explanation for lost strength, but they are a plausible and increasingly studied piece of it.

Why mitochondria sit at the center of the conversation

Healthy cells do not simply build mitochondria and leave them running forever. They continuously recycle the ones that become damaged or inefficient, a housekeeping process called mitophagy, a specialized form of autophagy aimed specifically at mitochondria. When mitophagy works well, worn units are cleared and replaced; when it slows, damaged mitochondria can accumulate and drag down a cell's energy output. You can read a plain-language explainer of this in our what is mitophagy guide and more on the broader topic in our mitochondrial health overview.

This is where urolithin A enters. Urolithin A is not found in meaningful amounts in food directly. It is a gut postbiotic: your microbiome makes it from ellagitannins, compounds concentrated in pomegranates, walnuts, and certain berries. Only some people carry the bacterial species needed to convert ellagitannins into urolithin A efficiently, which means two people eating the same handful of walnuts can end up with very different internal levels. In laboratory and human research, urolithin A has been studied for its ability to support mitophagy, in effect helping cells clear worn mitochondria so healthier ones can do the work.

What the strongest human evidence shows

Urolithin A has moved further into human testing than many longevity-adjacent ingredients, which is worth taking seriously, though the field is still young.

Safety and the first human signal (human)

Andreux and colleagues published the first-in-human study in Nature Metabolism in 2019. It reported that urolithin A was safe and well tolerated at single doses up to 1,000 mg per day and, notably, that supplementation shifted a mitochondrial gene-expression signature in participants' muscle and blood in a direction consistent with improved mitochondrial biology. This was an early, mechanism-focused study rather than a strength trial, but it established a reasonable safety envelope and a biological rationale.

Muscle endurance and strength in adults (human)

Two later randomized trials looked at function more directly. Liu, D'Amico and colleagues (JAMA Network Open, 2022) studied older adults over roughly four months and reported improvements in measures of muscle endurance, alongside favorable changes in certain plasma markers, without meaningful gains in peak strength in that particular design. Singh and colleagues (Cell Reports Medicine, 2022) tested 500 mg and 1,000 mg daily arms in middle-aged adults over four months and reported benefits in muscle strength and aspects of exercise performance. Together these suggest urolithin A may support how muscle performs and resists fatigue, with effects that build over months rather than days.

Newer human signals worth watching

More recent work has widened the picture. A 2024 randomized controlled trial in the Journal of the International Society of Sports Nutrition studied resistance-trained men over eight weeks and adds data in a younger, already-active population. A 2025 randomized controlled trial in Nature Aging reported that a roughly 28-day course supported the mitochondrial health of immune cells in midlife adults, part of the emerging interest in so-called inflammaging. A 2025 trial in distance runners extends the exploration into endurance athletes. These are promising, but they are individual studies with different populations, doses, and endpoints, so they are best read as a converging direction rather than a settled conclusion.

What preclinical research suggests (and its limits)

Much of the original excitement came from animal and cell work, which must be labeled clearly as preclinical. Ryu and colleagues (Nature Medicine, 2016) showed that urolithin A induced mitophagy, extended lifespan in the worm C. elegans, and improved muscle function in rodent models. That work is genuinely important as a starting point, but rodents are not people, and effects seen in a mouse do not guarantee the same result in a 70-year-old human knee or quadriceps. A 2024 systematic review in Ageing Research Reviews on targeting aging with urolithin A in humans reached a measured verdict: the human evidence is still emerging.